The UK now protects 38% of its seas by law. Yet the government’s own assessment shows that our oceans are not thriving.

In April, the Department for Environment, Food, and Rural Affairs (Defra) published its latest assessment of the health of our seas: the UK marine strategy report.

Of the 15 components of ocean health assessed, only two clearly meet the standard of good environmental status (GES) – the benchmark for healthy seas that the UK committed to achieving by 2020. The other 13 are failing, uncertain or getting worse.

This is despite the UK now having 377 marine protected areas (MPAs), sections of sea designated by law to protect wildlife and habitats. Protected areas are important, but the detail behind that impressive-looking map is sobering.

Marine mammals, such as Whales, dolphins, and porpoises are not judged to have achieved good status. A key reason for this is bycatch: they are being accidentally caught and killed in fishing nets meant for other species.

Seabird populations are declining, with fewer chicks surviving each breeding season as the fish they depend on become harder to find.

The types of fish living in our seas are changing for the worse, with the biggest cod disappearing while smaller species take their place.

The entire food web is under strain. The microscopic organisms that underpin ocean life, called plankton, are becoming less productive as seas warm, and that loss ripples upward through every species that depends on them.

On the seabed, fragile habitats such as seagrass meadows continue to be damaged by pollution and disturbance from shipping and boat activity.

Our seas are getting noisier, more polluted with heavy metals, and littered with waste on the seafloor.

There are some bright spots. The numbers of grey seals are stable or increasing. Beach litter is declining. Commercial fisheries have shown modest improvement, with the share of fish stocks being fished at sustainable levels rising, though it is still fewer than half.

But these gains are outweighed by the broader trajectory.

Why MPAs are not enough

Protected areas play an important role, but they cannot address the full range of pressures our seas face. Drawing a boundary on a nautical chart does not stop warm water crossing it. It does not filter out the nutrient runoff flowing in from agricultural land and overwhelmed sewage systems. It does not silence the increasing underwater noise from shipping and industrial activity. It does not prevent whales, dolphins and porpoises from being caught in fishing gear that operates both inside and outside these boundaries.

Climate change is perhaps the telling example. Sea temperatures around the UK have risen by roughly 0.3°C per decade over the past 40 years, with extreme underwater heatwaves becoming more common. The report acknowledges that this is already altering marine ecosystems, affecting everything from plankton at the base of the food chain to the distribution of fish species. No MPA can insulate its inhabitants from a warming ocean.

Land-based pollution is another pressure that flows straight through protected area boundaries. The report identifies food production and sewage treatment as major causes of nutrient enrichment, with increasing nitrogen inputs entering coastal waters. Heavy metals from legacy mine contamination, particularly in Wales, continue to pollute the marine environment. Contaminants have not met good status because lead, mercury, copper and zinc remain above environmental thresholds.

What ocean recovery actually requires

None of this is an argument against marine protected areas. Well-managed MPAs are an essential tool, and recent proposals to ban bottom trawling in some protected sites are welcome.

But if we are serious about ocean recovery, we need to tackle root causes. That includes reducing agricultural and urban runoff and sewage discharges into rivers and coastal waters. The climate crisis is reshaping our marine ecosystems from the bottom of the food chain upwards so tackling greenhouse emissions is a key step. Managing underwater noise from an increasingly industrialised seascape is essential. And enforcing meaningful fisheries management will reduce bycatch and protect whole ecosystems, not just commercial stocks.

The government’s own environmental watchdog, the Office for Environmental Protection, has reached a similar conclusion. In September 2025, it identified possible serious failures by Defra to comply with environmental law in relation to the missed GES target, and launched a formal investigation. It is now asking the government to produce an evidenced, resourced and time-bound delivery plan.

When even the body set up to hold government to account on the environment is questioning whether the law has been broken, it is hard to argue that the current approach is working.

The UK was supposed to have achieved good environmental status in our seas by 2020. Six years past that deadline, this report shows we are still far from it. We cannot afford to let the percentage of protected areas on a map be a substitute for the hard and messy work of actually making our oceans healthy.

Heidi McIlvenny receives funding from the National Environment Research Council, the Department of Agriculture, Environment and Rural Affairs, and Ulster Wildlife. She is affiliated with the IOLN, RSPB, National Trust, and Ulster Wildlife.

Each spring, birds across America are in full voice. Cardinals chatter, sparrows sing and warblers warble. Birdsong lifts the human spirit – “‘Hope’ is the thing with feathers,” after all. Yet birds are not singing to soothe our nerves after a stressful day at the office. Instead, they sing to defend their territories and attract mates.

The traditional view of birdsong focuses on the male bird: He is like a gladiator who fiercely defends his territory against rivals to ensure sufficient space and resources to feed and raise his chicks.

Female birds, on the other hand, are often thought to be quiet spectators when it comes to territorial defense. This holds true for the red-winged blackbird and many other North American birds.

But it is far from the complete picture.

Female rose-breasted grosbeaks and many other birds sing and defend territories across the globe.

The growing recognition that females often participate in territorial defense leads to a puzzle: If two is better than one, why do male-female pairs cooperate to defend territories in some species, while just the male defends home turf in other species?

To find out, we performed over 3,000 playback experiments across the Americas, playing recorded bird songs from the same species so the bird would think it was hearing an intruder.

We measured territory defense in 264 species. By studying many types of birds in many different environments, we were able to figure out some answers.

Simulating a bird intruder

Humans are well aware of their property lines and don’t take kindly to intruders. Imagine you are relaxing at home and you see your neighbors digging in your flower garden. You might rush out to tell them to stop; your prize dahlias aren’t for them to take.

For birds, these sorts of disputes happen all the time, with territory owners engaging in song battles with neighbors. The songbirds aren’t just defending their garden. They’re defending their food resources, nest locations and even their mates from rival birds, within territories that often span several acres in size.

To study how birds defend their territories, we pretended we were an intruding bird. But because we can’t sing like the average bird, we used technology.

We surreptitiously placed a speaker in a bird’s territory, hid in the bushes nearby, and then broadcast that bird species’ song. We then counted how many individuals came out from other parts of their territory to respond to the speaker. Some sang at the sound, clearly agitated. A few tried to attack the speaker itself.

At the end of a two-minute experiment, we would leave – and the rightful territory owner presumably felt proud that it had successfully repelled the invisible intruder. Then, we analyzed variables that could explain why some female birds participate in territory defense while others stay out of the fray.

Birds that hang out together defend together

Some birds stick with their mate for life, while others pair up just for one short breeding season.

Studies have found that birds in long-term relationships cooperate in many daily tasks, whether it’s foraging for meals, gathering nest materials or feeding the babies.

We found that this cooperation extends to guarding their home.

Females in species with long-term bonds that last for years, such as Carolina chickadees, often defended their territory.

However, among pine warblers and other species that form temporary pairs only during the breeding season, males typically took responsibility for defending the territory.

Some families took it one step further by including the kids.

The brown-headed nuthatch might look cute and sound like a squeaky toy, but these birds are no joke when they team up to defend their territory.

The nuthatches employ the previous seasons’ offspring as nannies – nest helpers that help take care of their babies. We often saw three or more adult nuthatches attacking the speaker to defend their territory when we conducted playback experiments on this species, meaning that the mated pair was joined by at least one helper. It seems to be a good strategy to get the whole family involved in territory defense too.

There were some exceptions to these patterns. When we simulated invasions on the territory of the blue grosbeak, a species thought to be monogamous during breeding season, in multiple instances only the female bird defended the territory.

No time to relax in the tropics

Location also matters when it comes to bird defenses.

In the rainforests of Costa Rica and the mountains of Peru, we found that males and females cooperating to defend their territory together was generally the rule.

While humans living in places with cold winters associate tropical climates with vacations, birds living near the equator are not afforded the luxury of rest. Instead, they need to stay vigilant year-round to ward off any birds looking to usurp their resource-rich habitats. The need for year-round territorial defense may mean that teaming up is the best strategy to ward off competitors.

Lots of bird personalities

You might think it would get boring observing bird behavior day after day. And, indeed, we dealt with heat and humidity, hordes of biting insects, and early morning wake-ups.

But every experiment brought a peek into the personalities of these birds. There were the pugnacious tufted titmice, which seemed as if they were eagerly awaiting an opportunity to fight, given how quickly they came in to investigate the apparent intruder, and the nonchalant American robins, which took their sweet time in responding, only briefly peering at the speaker before returning to their daily routines.

Our adorable feathered friends are not afraid to get up close and personal with anything they deem a threat, either, including any gadgets. Many times we’d see small birds such as chipping sparrows scrapping with a speaker twice its size. The birds focus on the song, and it can take birds a while before they realize the speaker is not, in fact, a rival bird.

Male birds sing and defend territories, but so do many female birds. We found that cooperative territorial defense is especially common in birds with long-term social bonds or that live close to the equator.

So, the next time you hear birds singing as you walk around your neighborhood, listen closely to what each voice is really saying – and who is doing the singing.

Benjamin Freeman receives funding from the David and Lucille Packard Foundation

Shreyas Arashanapalli does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.